Ageing Effect on Availability of a Typical Emergency Diesel Generator using Dynamic Reliability Block Diagram

Ageing Effect on Availability of a Typical Emergency Diesel Generator using Dynamic Reliability Block Diagram

Emergency diesel generators are in stand-by status during nuclear power plants (NPP) normal operation. So it is necessary to ensure about their operability in a periodic manner. Due to their long standby mode, one of the main factors which could affect component reliability is ageing. Ageing becomes an eminent subject as average age of operating nuclear plants in the world is passing over 25 years. In this paper, dynamic reliability block diagram (DRBD) is used as one of dynamic approaches in reliability assessment of a critical component emergency diesel generator station (EDGS), which its unavailability was highlighted in Fukushima accident. It is vital to consider ageing effects in the calculations by choosing an appropriate time dependent reliability distribution. Time-dependent reliability models have been used to investigate EDGS’s reliability. At the end, by implementing Monte Carlo simulation and considering maintenance policy, availability of the system is calculated for 30 years operation of a typical NPP EDGS.